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| United States Patent |
5,031,873
|
|
Rau
|
July 16, 1991
|
Vehicular powertrain mount assembly
Abstract
A vehicular powertrain mount assembly comprising two metal bracket members
and a volume of a resilient elastomeric material sandwiched between and
adhesively bonded to the two brackets. An epoxy adhesive is used in
bonding the metal to the elastomer producing a bond having a minimum
tensile rupture strength of 3,000 Newtons when tested by ASTM D-429.
| Inventors:
|
Rau; Thomas E. (Dayton, OH)
|
| Assignee:
|
General Motors Corporation (Detroit, MI)
|
| Appl. No.:
|
463734 |
| Filed:
|
April 4, 1990 |
| Current U.S. Class: |
248/632; 29/897.2; 248/634; 248/638 |
| Intern'l Class: |
F16M 013/00 |
| Field of Search: |
29/897.2,450,451
156/313
248/632,633,634,638
|
References Cited
U.S. Patent Documents
| 3859239 | Jan., 1975 | Van Gils | 525/119.
|
| 4311204 | Jan., 1982 | Shupert | 180/54.
|
Primary Examiner: Echols; P. W.
Assistant Examiner: Bryant; David P.
Attorney, Agent or Firm: Tung; R. W.
Parent Case Text
This is a division of application Ser. No. 07/387/413, filed on July 31,
1989, which is a continuation of application of U.S. Ser. No. 197,948
filed May 24, 1988, which is being abandoned.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A vehicular mount assembly for resiliently supporting a powertrain
member on a frame member in a motor vehicle comprising:
a first bracket member;
means for securing said first bracket member to said powertrain member,
a second bracket member,
means for securing said second bracket member to said frame member,
a volume of a vulcanized elastomeric material having a first and a second
surface sandwiched between said first and said second bracket member,
a layer of a non-water-based thermoset adhesive between said first bondable
surface of said elastomeric material and said first bracket member, and
a layer of a non-water-based thermoset adhesive between said second
bondable surface of said elastomeric material and said second bracket
member.
2. A vehicular mount assembly for resiliently supporting a powertrain
member on a frame member in a motor vehicle comprising:
a first bracket member,
means for securing said first bracket member to said powertrain member,
a second bracket member,
means for securing said second bracket member to said frame member,
a volume of a vulcanized elastomeric material having a first and a second
surface sandwiched between said first and said second bracket member,
a layer of a non-water-based thermoset adhesive between said first bondable
surface of said elastomeric material and said first bracket member, and
a layer of a non-water-based thermoset adhesive between said second
bondable surface of said elastomeric material and said second bracket
member,
said layers of non-water-based thermoset adhesive having a sufficient bond
strength capable of surviving a continuous vehicular service temperature
of 220.degree. F.
Description
FIELD OF THE INVENTION
The present invention generally relates to a vehicular powertrain mount
assembly comprising two bracket members and a volume of a resilient
material sandwiched therein and, more particularly, is concerned with a
vehicular powertrain mount assembly comprising two bracket members and a
volume of a resilient material sandwiched between and adhesively bonded to
the two brackets.
BACKGROUND OF THE INVENTION
A vehicular powertrain mount assembly is usually known as an engine mount,
a transmission mount, or the like. When an internal combustion engine
powers a motor vehicle, there are numerous vibrations set up such as
jounce vibrations, fore and aft vibrations, and torque and torque reaction
vibrations. It is a customary practice to isolate these vibrations from
the passenger compartment by using resilient powertrain mounts. Powertrain
mount assemblies are also used to support a powertrain member on a
vehicular frame to provide for jounce and roll control of the powertrain
member relative to the frame. In a conventional powertrain mount assembly,
two or more bracket members are bonded to a volume of a resilient material
by adhesive means. The bracket members are normally stamped cold-rolled
steel parts which can be attached by mechanical means to either the
powertrain member or the frame member of a vehicle A typical resilient
material used in a powertrain mount assembly is a rubber material capable
of absorbing most of the vibration from the powertrain member and the
jounce from the frame member such that they are sufficiently isolated from
each other. The type of rubber materials normally used are natural rubber,
styrene-butadiene rubber, ethylene-propylene-diene-monomer rubber, and any
other suitable elastomeric materials.
The bonding of the rubber material to the metal bracket is ordinarily
accomplished with a solvent-based adhesive that is applied to the metal
prior to the rubber molding process and then co-vulcanized with the rubber
during the cure cycle. This is frequently called an in-mold bonding
process. Numerous problems are associated with the in-mold bonding process
and its resulting product. A first problem is the costly rubber-removal
operation. In a contemporary mount design with complicated rubber block
shapes and interlocking structures, it is impossible to seal rubber from
certain forbidden areas. Subsequent operations to remove the unwanted
rubber are labor intensive. Moreover, a secondary phosphating operation is
required to replace the phosphate coating. removed with the rubber flash.
Secondly, in an in-mold bonding process, metal brackets must first be
placed in a mold cavity prior to the rubber vulcanization process. This
greatly reduces the number of cavities allowed in a given mold size. The
mold is frequently damaged from improperly positioned metal brackets.
Furthermore, the mold cycle time of the mount assembly is increased
because cold brackets must first be heated in the mold.
Thirdly, there is a significant amount of solvent emissions from the
in-mold bonding process due to the solvent-based adhesive used. In most
cases, the use of expensive recovery equipment is necessary to meet air
pollution regulations.
It is therefore an object of the present invention to provide a powertrain
mount assembly that can be bonded together after the rubber block is first
vulcanized.
It is another object of the present invention to provide a
post-vulcanization bonded powertrain mount assembly that can be bonded
together by an inexpensive process suitable for use in a production
environment.
It is yet another object of the present invention to provide a
post-vulcanization bonded powertrain mount assembly comprising two bracket
members and a volume of a rubber material sandwiched between and bonded to
the two brackets by an epoxy adhesive.
SUMMARY OF THE INVENTION
My novel invention is a powertrain mount assembly comprising two bracket
members and a volume of a rubber material sandwiched therein and bonded to
the brackets by an epoxy adhesive. The rubber material is vulcanized prior
to the bonding process. The epoxy adhesive can be cured slowly at room
temperature or can be cured quickly at elevated temperatures. The epoxy
adhesive allows the use of a very low bonding pressure applied on the
metal brackets during the adhesive cure cycle This is a great process
advantage in that no bulky fixtures are required for the bonding process
and furthermore, deformation of the rubber material can be avoided. My
novel post-vulcanization bonded powertrain mount assembly can be cured at
a lower temperature and in a shorter time than the conventional
solvent-based adhesive bonded mount assembly. My post-vulcanization bonded
powertrain mount assembly can be manufactured with essentially no
deformation in the rubber block resulting in a more consistent product.
More design freedom in the rubber block shapes in my post-vulcanization
bonded mount assembly is achieved since more complicated shapes of rubber
blocks can now be used.
I have further discovered that the use of an epoxy adhesive between rubber
and metal in a powertrain assembly, i.e. a dynamic loading application,
taught by the present invention produces a greatly unexpected result. I
use the words "dynamic loading application" to describe applications in
which the loading on the part is of a dynamic or a consistently changing
nature instead of a static load which does not change. All powertrain
mounts previously have been bonded with solvent based rubber adhesives.
To someone skilled in the art in making powertrain mounts it would have
been obvious that, in order to survive a dynamic loading condition, the
adhesive joint itself must remain flexible and thus producing an impact
resistant joint interface between rubber and metal. The adhesive joint
produced by an epoxy adhesive is by no means flexible; instead, it is a
very rigid joint. It is, therefore, entirely unexpected to the inventor
that a rigid adhesive joint produced by an epoxy adhesive could survive in
a dynamic loading application.
This greatly unexpected result is further supported by Anderson, U.S. Pat.
No. 4,198,037 in that, in his dynamic loading application, he concluded
that no commercially available adhesive system could produce an acceptable
adhesive bond in his elastomer compression spring. The only method
Anderson found possible for bonding polyester elastomer to metal plates
was to cause the elastomer to flow into the apertures in the plates
forming a mechanical lock.
DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention will become
apparent upon consideration of the specification and the appended drawings
in which:
FIG. 1 is a perspective view showing a powertrain mount assembly.
FIG. 2 is a cross sectional view taken along 2--2 in FIG. 1 showing the two
joint interfaces between the rubber block and the two metal brackets.
DESCRIPTION OF THE PREFERRED EMBODIMENT
My novel invention is a vehicular powertrain mount assembly comprising two
bracket members and a volume of a rubber material sandwiched therein and
bonded to the brackets by an epoxy adhesive. I have discovered that by
bonding a vulcanized rubber block to metal brackets using an epoxy
adhesive resulted in a powertrain mount assembly having superior
properties and processing advantages.
Referring initially to FIG. 1, where a typical engine mount assembly 10 is
shown. A first metal bracket member 20 and a second metal bracket member
40 are bonded to a volume of rubber material 30 by adhesive means. The
adhesive used in our preferred embodiment is a two-part epoxy adhesive
shown in FIG. 2 at joint interface 26 and 46. Mechanical means for
securing engine mount assembly 10 to an engine (not shown) and a vehicular
frame member (not shown) are shown at 22 and 42 in FIG. 1.
In our assembly process, a volume of a rubber material (commonly known as a
rubber block) is first compression molded in a press. A mold release is
used which does not leave any residue on the rubber surface. I have
successfully used rubber material such as natural rubber and
ethylene-propylene-diene-monomer rubber for my powertrain mount
assemblies. Other suitable rubber materials such as styrene-butadiene
rubber, nitrile rubber, or the like, works equally well in my mount
assemblies. I have used a silicone type mold release material which can be
sprayed and cured on the mold surface. The rubber block surface to be
bonded is normally primed with a material that makes it compatible with
epoxy adhesives. For natural rubber, I have found a primer under the
tradename of Chemlok.RTM. 7701 supplied by the Lord Corporation worked
very well. Chemlok.RTM. 7701 is a solution of an organic acid which can be
sprayed or brushed on the rubber surface and then dried at room
temperature for five minutes.
The epoxy adhesive I used is a two-part structural grade epoxy adhesive
supplied by the Lord Corporation under the tradename of Fusor.RTM. 320
resin and Fusor.RTM. 310B hardener. A structural grade adhesive is one
that can be used in applications where there are high stress loading
conditions. The mix ratio I have used is ten parts resin to five parts
hardener which resulted in a higher softening temperature than that
specified by the manufacturer after cure. Fusor.RTM. 320 resin is a
bisphenol-A type epoxy resin having a viscosity between 250,000 to
1,000,000 CPS as determined by a Brookfield viscometer at 25.degree. C.
with T-Bar-C at 5 RPM. It has a density (weight per gallon) between 11.7
to 12.7 oz. The Fusor.RTM. 310B hardener is a mixture of a polyamide resin
(60 to 70%), an aliphatic amine (2-7%), and aluminum powder (15-20%). It
has a viscosity between 200,000 to 450,000 CPS as determined by the
Brookfield viscometer at 25.degree. C. with T-Bar-C at 5 RPM. It has a
density (weight per gallon) between 10.1 to 10.5 oz.
I have used other types of structural adhesives that worked equally well in
my novel invention. These include Epoxy Patch.RTM. 9340 supplied by the
Hysol Division of Dexter Corporation, Epon.RTM. 828 resin supplied by the
Shell Corporation cured by Versamid.RTM. 140 supplied by the General Mills
Corporation. Other non-epoxy type structural adhesives such as
polyurethane base adhesives may work equally well. One of such adhesives I
have used successfully is Tyrite.RTM. 7500A and Tyrite.RTM. 7510B supplied
by the Lord Corporation.
After Fusor.RTM. 320 and Fusor.RTM. 310B are mixed together, it has a shelf
life between 20 to 30 minutes. Within this time, the adhesive is applied
to either the rubber surface or the metal bracket surface. After the
rubber block and the metal brackets are put together, a low pressure (less
than 5 PSI) is applied to the assembly normal to the bond planes. The
pressure should be sufficient to spread the adhesive in the joint
interface and extrude a small amount from the edges. The powertrain
assembly under pressure is then subjected to a heating medium such as hot
air or infrared such that the bondline temperature reaches 250.degree. F.
for one minute. It can also be cured at room temperature in approximately
24 hours. After the adhesive is cured, the bonded powertrain assembly is
removed from the fixture and ready for packaging and shipment.
My novel powertrain mount assembly bonded by an epoxy adhesive can be
assembled easily and can be used at continuous service temperature as high
as 220.degree. F. It has passed a vehicular service test at 220.degree. F.
for six days under maximum engine load conditions.
My post-vulcanization bonding process produces powertrain mount assembly
having superior tensile rupture strength when compared to those bonded by
the conventional in-mold bonding technique. I have conducted laboratory
adhesion tests performed in accordance with the American Society of
Testing and Materials (ASTM) test D-429 (method A). In this test, rubber
is bonded between two parallel metal discs that are one inch in diameter.
The two metal discs are then pulled apart in a tensile testing machine to
determine the tensile rupture strength of the bond.
For comparison, I have tested several commercial adhesives used in both the
conventional in-mold bonding method and my novel post-vulcanization
bonding method.
TABLE 1
______________________________________
TENSILE RUPTURE STRENGTH, NEWTONS
POST-
IN-MOLD VULCANIZATION
SAMPLE BONDING BONDING
______________________________________
Chemlok .RTM. 236
1,378 1,150
Chemlok .RTM. 238
1,356 --
Thixon .RTM. OSN-2
1,751 --
Chemlok .RTM. TS3604-72
3,370 --
Fusor .RTM. 320/310B 3,846
______________________________________
Chemlok .RTM. adhesives are supplied by the Lord Corporation. Thixon .RTM
adhesives are supplied by the Dayton Chemical Company. In Thixon .RTM.
OSN2 bonded samples, the bond strength or the tensile rupture strength of
the bond is lower than usual since the samples tested were prepared with
metal discs that were not phosphated. samples, the bond strength or the
tensile rupture strength of the bond is lower than usual since the samples
tested were prepared with metal discs that were not phosphated.
It is seen from Table 1 that epoxy post-vulcanization bonded samples
(Fusor.RTM. 320/310B) showed higher bond strengths than all the other
samples bonded with solvent-based rubber adhesives. It pulled
approximately 15% higher than the best of the four adhesives tested with
conventional in-mold bonded techniques, and also showed about 300% better
strength than the samples post-vulcanization bonded by the conventional
solvent-based rubber adhesive.
I have found that with epoxy post-vulcanization bonded samples, the tensile
rupture strength obtained in ASTM D-429 test was consistently over 3,000
Newtons. Even though in-mold bonded Chemlok.RTM. TS3604-72 test samples
also show an average tensile rupture strength of over 3,000 Newtons, many
individual test samples were tested at strength values of under 3,000
Newtons. It is therefore my conclusion that only epoxy post-vulcanization
bonded samples consistently show an improved bond strength in powertrain
mounts.
While my invention has been described in terms of a preferred embodiment
thereof, it is to be appreciated that those skilled in the art will
readily apply these teachings to other possible variations of the
invention.
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